Results 1 to 5 of 5

Math Help - Separable differential equation problem

  1. #1
    s3a
    s3a is offline
    Super Member
    Joined
    Nov 2008
    Posts
    597

    Separable differential equation problem

    Could someone please take a look at "#6 (Again)" from the attached PDF file and tell me if something stands out as wrong because I keep getting the wrong answer? If you're lazy (or whatever the reason is) but you see my mistake(s), you don't have to explain to me how to do it but just tell me where the mistake(s) is/are and I will try to figure it out myself.

    Any input would be greatly appreciated!
    Thanks in advance!
    Attached Files Attached Files
    Follow Math Help Forum on Facebook and Google+

  2. #2
    A Plied Mathematician
    Joined
    Jun 2010
    From
    CT, USA
    Posts
    6,318
    Thanks
    5
    Awards
    2

    Re: Separable differential equation problem

    Your problem isn't the initial solution, but in plugging in the initial condition. The equation

    0=C_{1}^{2}-6C_{1}+7 should be

    0=C_{1}^{2}-6C_{1}-7.

    You tried too many steps at once in getting to that equation, and then forgot that you didn't actually flip the sign of the RHS.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    s3a
    s3a is offline
    Super Member
    Joined
    Nov 2008
    Posts
    597

    Re: Separable differential equation problem

    I still get C1 = 3 +/- sqrt(2)

    (The modified version - as of the step you corrected - of the previous PDF is attached).
    Attached Files Attached Files
    Follow Math Help Forum on Facebook and Google+

  4. #4
    s3a
    s3a is offline
    Super Member
    Joined
    Nov 2008
    Posts
    597

    Re: Separable differential equation problem

    I caught the last mistake I had. This time I had rooted the b^2 - 4ac part twice in the quadratic formula. Thanks.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    A Plied Mathematician
    Joined
    Jun 2010
    From
    CT, USA
    Posts
    6,318
    Thanks
    5
    Awards
    2

    Re: Separable differential equation problem

    You're welcome! Have a good one.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 4
    Last Post: March 23rd 2010, 03:10 PM
  2. separable differential equation y'=y^2 sin x
    Posted in the Calculus Forum
    Replies: 3
    Last Post: March 18th 2009, 05:02 AM
  3. Help with this separable differential equation problem
    Posted in the Differential Equations Forum
    Replies: 1
    Last Post: January 29th 2009, 10:30 AM
  4. Another separable differential equation
    Posted in the Differential Equations Forum
    Replies: 3
    Last Post: October 5th 2008, 05:35 PM
  5. separable differential equation
    Posted in the Differential Equations Forum
    Replies: 3
    Last Post: October 5th 2008, 02:51 PM

/mathhelpforum @mathhelpforum